1. Technical Field
The invention relates to devices for connecting the shell or face piece of an oral-nasal breathing mask to a helmet of the type comprising two fasteners, each placed on one side of the median vertical plane of the helmet and one at least of which is provided with a quick fastening and unfastening attachment device.
2. Prior Art
Devices of the above defined kind are very widely used in military aeronautics, for connecting the breathing mask required for high altitude flights to the helmet worn by the crew members. In known devices, such as those described in the documents US-A-3 035 573 and GB-A-894 747, the fasteners comprise a continuous strap passing over the shell of the face cover of the mask at a relatively high level. The shell of the mask is arranged for fitting over the chin and a second strap for connection to the helmet passes under the mask so as to retain it, particularly in the case of bailing out.
This arrangement has been very likely adopted, almost universaly in present day fighter aircraft, because it was thought necessary for fitting the mask sufficiently sealingly against the face of the wearer. But it has therefore drawbacks, the seriousness of which seems not to have been appreciated up to now. Due to the deformable nature of the straps, there is a danger of leaks appearing between the face and the shell when the mask is fed at a high overpressure with respect to the ambient atmosphere. When the pilot is subjected to high accelerations, there is a danger of the mask slipping downwards. The strap, which is placed very high, impairs the downward vision field of the wearer. Furthermore, it is known that one of the problems impeding use of a helmet aiming unit is the danger of the helmet moving during movements of the head, the presence of the mask being unable to prevent such sliding due to the flexibility of the straps.